Centralized radio system



Aug. 1, 1933 .1. L. WHITTAKER CENTRALIZED RADIO SYSTEM Original Filed Dec. 11, 1930 5 Sheets-Sheet l ooooowo MT ooooooonww 00 0000 00000000 00000 0 I ooooooo w I ooooo o m o\ooo o 0 9000000 mooooooofiwi l7 //.||ll

lNVENTOR ATTORNEY Aug, 1, 1933 J. L. WHITTAKER v CENTRALIZED'RADIO SYSTEM 3 Sheets-Sheet 2 Original Filed Dec. 11, 1930 MR9. EQRQ K 7 4 Z ATTORNEY M 1, 1933. WHITTAKER 1,920,775

CENTRALIZED RADIO SYSTEM Original Filed Dec. 11, 1930 5 Sheets-Sheet 3 P06/ T/ON OFF P051 77 ON P0-Sl 77 ON 0 O O N q) 39b 52 g Q Q 5 OFF 3 INVENTOR ATTORNEY @atented Aug. 1, 1%33 TATEg or ies GENERALIZED RAIMM) SYSTEM Application December 11, 1930, Serial No. 501,551

Renewed @ctober 28, 1932 13 Claims. (oi. rad i) The present invention relates to centralized electrical control systems and has to do particularly with centralized radio systems, that is, radio systems which comprise a plurality of loud speak- 5 ers or sound radiating elements which are located at diiferent places but which are wholly or partially operated or controlled from some central point.

Centralized radio systems have achieved a position of considerable importance in such uses as schools, hotels, and the like. In systems of this kind, a number of loud speakers are placed at various different points where it is desired that the programs shall be heard. In school or hotel use, for instance, a loud speaker is placed in each room or in such of the rooms as desired. In the larger rooms, for examplaauditoriums, dining rooms, lobbies, etc., several speakers can be placed about the room to provide for proper volume and proper distribution of sound. The size and kind of loud speakers placed at different points will depend upon the service required of the respective speakers. Each of the individual loud speakers is ordinarily wired so that it can be operated to receive any one of a number of programs, and each loud speaker or loud speaker circuit is provided with a selector switch by means of which the desired program can be selected. By way of illustration, a hotel may provide its guests with a choice of say two radio programs.

In such a system two radio sets are provided in the hotel, and these two sets are tuned in on the two desired radio programs. An amplifier sufiiciently large to supply all of the speakers which 3 may be connected on either of the program circuits at any one time is provided in connection with each radio set, and the outputs from the respective amplifiers are made available to the various individual speakers by means of appro- 40 priate circuit wiring. Thus, the two programs are received and amplified at a central point and are distributed from that point to the individual speakers, the selector switch provided for each individual loud speaker or loud speaker circuit being used to select whichever of the several programs is desired or to cut the loud speaker off of all of the programs. While the individual selector switches are ordinarily placed in the rooms with the respective loud speakers, they may be placed elsewhere and, if desired, may be grouped together at a central point.

The present invention relates principally to improvements in the design, arrangement, wiring and operating control of centralized systems of r the general class indicated above, which improvements aiiord certain important advantages as fully stated and described below. It is an object of the present invention to provide a centralized radio system which can be designed and built to distribute any desired number of pro- 0 grams to any desired number of individual loud speaker circuits extending to various points as desired, which system operates satisfactorily irrespective of the number of speakers which may be in operation at any time and irrespective of 5 the relative division of the operating speakers among the several program channels.

It is also an object of the invention to provide a centralized radio system of this character which comprises a master switch that can be operated to throw all of the loud speakers of the system simultaneously on to any desired one of a number of program channels.

It is also an object of the invention to provide a system of the character just indicated which comprises a master switch and individual selector switches for independently controlling the respective loud speaker circuits. The master switch can be operated to deliver any desired one of the several programs to all of the individual loud speakers simultaneously irrespective of the settings oi the individual selector switches. When the master switch is operated to connect all of the loud speakers on to one of the program channels, the individual selector switches are rendered inoperative, and each individual loud speaker is caused to operate on the particular program selected by the master switch. The master switch is preferably provided with a number of positions equal to the number of primary program channels which the system comprises, so that it can be used to deliver the program from any one of the several program channels to all of the loud speakers, and the master switch is further provided with an additional or neutral position and is so connected in circuit with the respective individual selector switches that, when it is in its neutral position, the several programs are delivered to the individual selector switches and these switches become operative as program selectors for the respective loud speaker circuits.

It is a further object to provide a system of the character indicated above which does not require that the individual loud speaker or load circuits be brought directly backto the master switch. Important results of this feature of the invention are the great reduction in wiring required for the system and thefact the. the size and number of sections required in themasterswitch are determined by the number of program channels which the system is designed to handle and are independent of the number of loud speaker circuits included in the'system. The master switch can be of small size, a large number of loud speaker or load circuits can be handled and load circuits can be added to or removed from the system without any change in the master switch or its wirlIlg- It is a still further object of the invention to provide a system of the class referred to above wherein each loud speaker circuit may consist of a single pair of wires, this single pair of wires serving to deliver different programs to the speaker at different times, depending upon the settings of the master switch and the respective individual selector switches. If, desired, the master switch and individual selector switches may be located at, a central point, the master switch being placed between the output circuits of the amplifiers and the program input to the individual selector switches. Since the respective load circuits may serve loud speakers in widely separated rooms, or even in different buildings, the invention provides for great reduction in wiring cost by requiring only one pair of wires in each loud speaker circuit rather than requiring a number of pairs of wires equal to the number of program channels included in the system.- This arrangement also improves the operation of the system and permits the addition'of other program channels to the system without necessitating a change in the wiring which goes to the respective loud speakers.

It is a still further object of the invention to attain proper operation of the respective individual loud speakers, irrespective of the number thereof which are operating or which might be operating on any one channel, byproviding a substantially constant value of impedance in circuit with each program channel amplifier at all times when any speaker is or could be in circuit on that channel. The best operation is effected when the impedance of the load circuit is' properly matched to the impedance of the amplifier output circuit. The invention provides for load coils operating in conjunction with each load circuit, each coil being of impedance substantially equal to the impedance of the loud speaker or speakers provided on that load circuit, and further provides that these loadcoils may be controlled both by the master switch and the individual selector switches, the arrangement being such that whenever a certain loud speaker circuit is operating on a certain program channel no load coil corresponding to that speaker circuit will be operating on that channel but that whenevena certain loud speaker circuit is out 01f from a channel which is or may be in use by other speakers one and only one load coil is thrown on the channel in place of the loud speaker circuit which has been cut ofi, thus providing for substantially constant load impedance on the respective amplitiers. The manner in which this is effected will be described in detail below.

It is a still further object of the invention to provide a centralized radio system embodying the various novel features and advantages-referred to above which, in its preferred embodiment is compact, is made up largely of apparatus and parts which are of standard manufacture or which can be standardized so that the cost of the system is not excessive, is or can be controlled from a central point with all of the necessary control equipment assembled in a cabinet of design and size acceptable as good furniture in an office or room, is flexible after installation in the matter of modification to handle a greater or lesser number of load circuits, is susceptible of modification to handle an increased number of program circuits without changing or increasing the amount of circuit wiring to the individual speakers, and is adapted for use in receiving and distributing a plurality of programs selected from radio broadcasting stations or generated by a phonograph reproducer connected into the system or derived from a microphone connected into the system, or any combination of these, or other inputs.

The above stated objects and advantages are attained largely by the novel design, arrangement and combination of electrical circuits and other elements embodied in the system, all as will be fully described and illustrated in the following specification and in the drawings which are made a part hereof. In said drawings, Figure 1 is a perspective view of one form of control cabinet which may be employed in a centralized radio system embodying the present invention; Figure 2 is a diagrammatic view showing the control cabinet, the radio receiving and amplifying equipment and" the principal connections leading t6 and from the control cabinet; Figure 3 illustrates the general structural features of a type of selector switch which has been found satisfactory for the purposes of the invention; Figure 4 is a diagrammatic view showing the arrangement of electrical parts and wiring in an individual selector switch; Figure 5 is a diagrammatic view showing electrical parts and wiring in the master switch and an individual selector switch and the circuit wiring between the master switch and the individual selector switch; Figure I 6 is a diagrammatic view showing the complete electrical arrangement and wiring of an individual selector switch and its load circuit; and Figure 7 is a wiring diagram of the complete system of the invention.

For the purpose of disclosing the invention clearly, apreferred embodiment of the invention particularly adapted for the requirements of schools or the like is described below. It is understood that the particular system described in the specification and shown in the drawings is disclosed in detail for the purpose of illustrating and describing the invention, and that the invention is not thereby limited to the exact embodiment shown and described.

In the particular embodiment shown herein, the control apparatus for the system is assembled and mounted in a cabinet 10, here shown as a cabinet of design and size such that it constitutes an acceptable article of furniture for the oflice of the principal of the school or for any other room from which it is desired to control the system. Referring particularly to Figure 1 of the drawings, cabinet 10 comprises a portion or compartment having doors 11 which, when opened, reveal a panel 12 upon which a master switch 13 and various individualsclector switches 14 are mounted. The particularsystem. shown herein comprises three program input channers; i. e., the system is of a character such that three programs are available to each loud speaker in of example. In a three channel system, the mas-' ter switch 13 and each of the individual selector switches 14 have four separate positions,-an

"off or neutral position and three other positions related to the three program channels as described below. The respective switches are operated by turning them to the right or left, and the switches are so designed that their respective positions are well-defined and are readily apparent upon turning of the switch. The system is so designed that, when the master switch is turned into its off or neutral position, the respective individual switches are operative to control the respective loud speaker circuits and to select, program therefor. The program selection for each loud speaker circuit is independent of that for every other circuit. When the master switch is moved into any of its other positions, program from one of the three program channels is delivered immediately to all of the loud speaker circuits irrespective of the settings of the individual selector switches, and the individual selector switches are rendered inoperative as program selectors.

Panel 12 also carries a group of channel pilot lights 15, one for each program channel, to indicate which program channels are operating. Remote control power switches 16 may be provided, one for each program channel, so that the power for the respective channels can be turned on and 01f at the central control board. Microphone input jacks 1'7 and microphone control equipment 18 may also be provided. A microphone may be located at any point in the system as desired; e. g., in a lecture room, auditorium, or" the like, the leads from the microphone extending back into the central control room where they may be introduced into any one of microphone jacks 17 so that a program originating at the microphone can :be distributed throughout the system over any desired one of the program channels. Also, a phonograph reproducer (not shown) may be connected into the system to thereby furnish program for distribution over any one of the several program channels when desired. The lower portion or compartment 19 of cabinet 10 is a battery and cable compartment which houses the microphone battery and certain of the cables and connections requiredby the system. It will be understood that the particular shape and design of the control cabinet 10 is largely a matter of personal preference. The particular form of cabinet here shown is merely illustrative of one form which the cabinet mayassume so that it constitutes an acceptable piece of furniture which can be placed anywhere in the building.

Referring to Figure 2, three radio receiving stages and amplifiers, shown diagrammatically and indicated at 20, 21 and 22, are provided for the reception and amplification of program. These radio receivingunits and amplifiers are ordinarily placed in aspecial radio room either adjacent or remote from the control room as desired. Amplifiers 20, 21 and 22 deliver program output into control cabinet 10 over circuits or program channels indicated on the drawings as channel 1, channel 2 and channel 3. Each of these circuits or program channels consists of a single shielded pair of wires. These three pro-- gram channels 1, 2 and 3 enter cabinet 10 and are carried onto the master switch 13 as indicated. The construction and wiring of the master switch 13 and of the individual selector switches 14, and also the wiring between the master switch and the respective individual selector switches, is shown ;in detail in other figures of the drawings and will be described at length below. A single pair of wires 23- is led out from each of the individual selector switches 14 and constitutes the wiring for each loud speaker circuit or load circuit. One or more loud speakers 24 is connected in each load circuit 23 and, if desired, a volume control device 25 may be provided adjacent speaker 24. Also, a switch for opening and closing the load circuit may be provided adjacent speaker 24, although such a switch is not ordinarily preferred in a schooltype installation of the kind described herein and is therefore not shown in the accompanying drawings. It will be understood that any desired number of load circuits 23 can be provided, one individual selector switch 14in the control cabinet 10 being required for each load circuit. It will also be understood that one or more loud speakers 24 can be provided on each circuit 23,

and that the loud speakers on any given circuit may be in the same room or in different rooms as desired. For the purpose of facilitating explanation: of

the operation of master switch 13 and individual selector switches 14, a form of switch which has been found satisfactory for operation in this system will be described, it being understood that this particular form of switch (shown in Figure 3) is not of my invention and is not claimed herein. Each individual selector switch 14 is essentially a switching means by which the desired program from any one of the primary program channels 1, 2 or 3 can be selected and delivered to the loud speaker circuit which is controlled by that switch. Referring to Figure 3 which shows the structure of the switch and to Figure 4 which shows the wiring, each individual selector switch' 14 comprises two sliding contacts 26 which are permanently connected to the two sides of one of the load circuits 23. adapted to make contact with stationary "contacts 27. The two sliding contacts 26 move in unison so that, in any switch position, they are in contact with a pair of the stationary contacts 27, as shown, four pairs of contacts 27 being provided to thus form four switch positions, as shown particularly in Figure 4. The four switch positions are designated respectively from left to right as oil, 1, 2 and 3. The pair of contacts representing position 1 of the switch are connected to the two sides of program channel 1, the pair of contacts representing position 2 of the switch are connected to the two sides of program channel 2, and the contacts representing position 3 of the switch are connected to the two sides of program channel 3, all as particularly shown in Figure 4. The pair of contacts representaing the ofi position of the switch are connected to a pair of wires 48 which normally are not energized but which serve a purpose to be described below. Therefore, in normal operation, when sliding contacts 26 are in off position the load circuit 23 which is controlled by the switch is not energized, when contacts 26 are in position 1 program from channel 1 is delivered into the load circuit, when contacts 26 are in position 2 program from channel 2 is delivered into the load circuit, and when contacts 26 are in position 3 program from channel 3 is delivered into the load circuit. This situation prevails when the master switch is in off position, as it always is except when it is desired to deliver the program from one program channel to all of the load circuits simultaneously.

Reaerring to Figure 5 of the drawings, the

Sliding contacts 26 are" master switch is indicated diagrammatically and comprises four double pole sections indicated respectively at 30, 31, 32 and 33. Each of these sections is provided with four pairs of stationary contacts indicated at 30a, 31a, 32a and 33a, respectively. Each section of the master switch is provided with a pair of sliding contacts indicated respectively at 30b, 31b, 32b and 33b, all mounted on a common shaft and all moving in unison, this result being accomplished by a switch of the same general structure as that shown in Figure 3, it being understood that the master switch has four double pole sections whereas each individual selector switch has but one such section.

Program channel 1, which carries the output from amplifier 20, is connected to the respective stationary contacts of position 1 of the master switch as shown. Program channels 2 and 3 are similarly connected to the stationary contacts of positions 2 and 3 of the master switch as shown. The pair of stationary contacts in the off position of section 30 of the switch are connected to program channel 3 by means of a pair of leads 34; the pair of stationary contacts in the ofi" position of section 31 of the switch are connected to program channel 2 by means of a pair of leads 35; the pair of stationary contacts in the off position of section 32 of the switch are connected to program channel 1 by means of a pair of leads 36, all as diagrammatically shown on the drawings. The pair of stationary contacts in the off position of section'33 of the switch are not connected to either of the three program channels; these contacts have no direct connection with any of the electric circuits of the system.

The pair of sliding contacts 301) of section 30 of the switch are connected through a pair of leads 37 to another pair of leads 38, from which latter pair of leads connections 39 are brought out and connected with the pair of stationary contacts of position 3 of individual selector switch 14. The pair of leads 33 constitutes a feeder line for all of the individual selector switches 14 of the system, it being understood that any desired number of individual selector switches may be used. That is, channel 3 program is supplied from the master switch 13, through leads 37 to feeder line 38, and connections are made from line 38 to the stationary contacts in position 3 of each individual selector switch. Similarly, channel 2 program is supplied from master switch 13, through sliding contacts 31b and leads 40 to feeder line 41, and connections 42 are made from line 41 to the stationary contacts in position 2 of each individual selector switch. Also, channel 1 program is supplied from master switch 13, through sliding contacts 321) and leads 43 to feeder line 44, and connections 45 are made from line 44 to the stationary contacts in position 1 of each individual selector switch. Connection is made from the pair of sliding contacts 33b of section 33 of the master switch through leads 46 to a pair of leads 47 constituting afeeder line from which a pair of leads 48 is tapped off and connected to the stationary contacts of the off position of each individual selector switch. With the circuit arrangement described above and shown in Figure 5 of the drawings, placing of the master switch in its off position energizes the position 1 contacts of the individual selector switches with program from channel 1, energizes the position 2 contacts of the individual selector switches with program from channel 2, energizes the position 3 contacts of the individual selector switches with program from channel 3, and leaves the 011" position contacts of the individual selector switches dead. Thus, when the master switch is in its off position, the respective load circuits and the various loud speakers associated therewith are controlled entirely by individual selector switches 14, it being possible to operate each individual selector switch to energize its loud speaker circuit from any desired one of the'several program channels or to disconnect its loud speaker circuit from all program channels.

Further describing the operation of the system, if the master switch 13 be moved to position 1, sliding contacts 302) make contact with the position 1 stationary contacts of section 30 of the switch. Since these position 1 contacts of section 30 of the switch are energized from program channel 1, program from channel 1 will be sent out over leads 37, feeder line 38 and branch lines 39 to thereby energize all of the position 3 contacts of the individual selector switches 14 with program channel 1. Similarly, sliders 31b are brought into contact with the position 1 contacts of the master switch, and program from channel 1 is distributed through leads 40, feeder line'41 and ,branch lines 42 to thereby energize all of the position 2 contactsv of the individual selector switches 14 with program from channel 1. Also, sliding contacts 3219 are brought into engagement with the position 1 contacts of section 32 of the master switch, and program from channel 1 is distributed through leads 43, feeder line 44 and branch lines 45 to thereby energize all of the position 1 contacts of the individual selector switches 14 with program from channel 1. Also, sliding contacts 331) are brought into engagement with the position 1 contacts of section 33 of the master switch, and program from channel 1 is distributed through leads 46, feeder line 47 and branch lines 48 to thereby energize all of the 01f position contacts of the respective individual selector switches with program from channel 1. Thus, every position of each individual selector switch, including the off position, is energized with program from channel 1, and all of the load circuits and the loud speakers associated therewith immediately receive program'fromchannel 1 irrespective of the settings of the various individual selector switches. Also, since none of the position 1 contacts of the master switch are connected to channel 2 or channel 3, movement of the master switch into position 1 cuts off program channels 2 and 3 from all of the individual selector switches, so that any of the load circuits which have been receiving programs from channels 2 and 3 are automatically disconnected from those channels and are immediately placed on channel 1 to receive program therefrom. Similarly, movement of master switch 13 into position 2 serves to energize all of the loud speaker circuits of the system with program from channel 2; likewise, movement of the master switch into position 3 serves to energize all of the loud speaker circuits of the system with program from channel 3. I i

For the sake" of clarity the system described nel 2, some on channel 3 and some may,-not be operating at all. Also, at different timesfydifierthe several program channels.

ent numbers of loud speakers may be operating on any one channel. Because of considerations mentioned earlier in this specification, it is desirable for best operation that the load impedance into which the respective amplifiers operate be properly matched with the impedance of the input circuit and be maintained approximately constant. To this end each individual selector switch 14 is provided with a number of load coils equal to the number of program channels; viz., three, the impedance of each load coil being approximately equal to the effective impedance of the loud speaker or speakers which are operating on that load circuit. The arrangement of load coils and the operating connections between therespective load coils and each individual selector switch 14 are shown diagrammatically in Figure 6.

Referring to Figure 6, three load coils 50, 51 and 52 are associated with each individual selector switch 14. Load coil 50 is connected across the position 1 contacts of the individual selector switch 14, load coil 51 is connected across the position 2 contacts of the switch, and load coil 52 is connected across the position 3 contacts of the switch. One side of each load coil is pro-v vided with means by which the load coil circuit can be opened to thereby cut the load coil out of circuit. Referring to Figure 3 as well as to Figure 6, this load coil circuit opening device consists of. a pair of spring contacts 53 which are normally pressed together by their own spring action to thereby maintain the load coil circuit closed. An insulated member 54 is mounted on the same shaft that carries the sliding contacts 26. When the individual selector switch is moved into position 1, sliding contacts 26 come into engagement with the stationary contacts of position 1 and, at the same time, insulatingmember 54 enters between spring contact members 53 of load coil 50, thus spreading contacts 53 apart and opening the circuit which supplies load coil 50. From the above it will be seen, when any individual selector switch 14 is in off position and when the master switch 13 is in off position, that the loud speaker circuit of that individual selector switch is not energized but that load coil 50 is energized from program channel 1, load coil 51 is energized from program channel 2 and load coil 52' is energized from program channel 3. Upon movement of the individual selector switch into position 1, the loud speaker circuit of the switch thereby becomes energized from program channel 1 and, simultaneously, load coil 50 is cut off of chann c1 1, its circuit having been opened by insulating member 54. Load coils 51 and 52 remain in circuit on program channels 1 and 2, respectively. Thus, when any loud speaker circuit is thrown on to any one of the program channels, the loud speakers pertaining to that selector switch become energized and the load coil pertaining to that switch and to the particular program channel being utilized is cut out of circuit. It will be observed that only that load coil corresponding to the particular program channel in use is out out of circuit, the load coils for the other two program channels remaining in circuit. This arrangement insures that all of the program channels are operating at an approximately constant load at all times irrespective of the number of speakers in operation and irrespective of the distribution of the speakers among As a matter of construction, the various load coils pertaining to the individual selector switches 14 are small compact units mounted as part of or in proximity to the bank of individual selector switches in the control cabinet 10.

The arrangement and operation of load coils described above and shown in Figure 6 suffices for all of the requirements of the system as long as the master switch is in its off or neutral position; i. e., in such position that the respective loud speaker circuits are controlled by the individual selector switches 14. However, a further control means for the load coils is necessary to preserve proper balance of the system when the master switch is thrown into position "1, position 2 or position 3 to thereby connect all of the loud speakers of the system on to one program channel. This arrangement is shown in Figure 7, which figure is a diagrammatic layout of a complete operating system representing a preferred embodiment of the invention. The system of Figure 7 is similar to that of Figure 5 with the addition of the load coils and the control means therefor. Themaster switch comprises four double pole sections 30, 31, 32 and 33, as shown in Figure 5, and in addition comprises three single pole sections indicated at 55, 56, and 57 in Figure 7.- Sliding contacts 55b, 56b and 57b operate over the four contact positions of sections 55, 56 and 5'7, as shown, in the same manner as sliding contacts 30b, 31b, 32b and 33b operate over the four positions of sections 30, 31, 32 and 33 of the switch, as above described. With the master switch in off position, the circuit of all load coils 50; i. e., of all load coils associated with program channel 1, is completed through section 55 of the master switch by way of lead a, slider 55b and lead 45b; the circuit of all load coils 51; i. e., of all load coils associated with program channel 2, is completed through section 56 of the master switch by way of lead 42a, slider 56b and lead 421); and the circuit of all load coils 53; i. e., of all load coils associated with program channel 3, is completed through section 57 of the master switch by way of lead 39a, slider 57b, and lead 391), all'as shown in Figure 7. Thus, when the master switch is in position off, the operation of all of the load coils is controlled by the operation of the respective individual selector switches as described above. When, however, the master switch is turned into position 1, position 2 or position 3, the circuits of all three load coils 50, 51 and 52 are broken by reason of the fact that sliders 55b, 56b and 57?) are moved out of engagement with the off position contacts of sections 55, 56 and 57 of the master switch, and the off position contacts are the only contacts in these sections of the switch which are in circuit with the rest of the system. Thus, when the master switch is moved into any position other than its off position, all load coils are cut out of circuit. It is necessary that all load coils be cut out of circuit because, with the master switch in positions 1, 2 or 3, program from one channel is supplied to all positions of each individual selector switch, and any load coil left in circuit at any individual selector switch would therefore become a load on the one program channel in use at the time. Since all speakers are in operation on thatv channel, the channel is fully loaded by the speakers and no further load is desired. It is understood that lead 45a is a common lead for one side of all load coils which operate in conjunction with program channel 1. Thus, when the load coil circuit is broken at b, all load coils 50 associated with channel 1 throughout the system are removed from cirin the system can be supplied with program from any desired one of the program channels. All or any number of the loud speaker circuits can be operated at one time, and any desired distribution of the speakers between the various program channels can be effected. The system comprises a master switch into which are led the several primary circuits or program channels of the system, and this master switch has a neutral or off position which effects distribution of program from the several program channels to the respective positions of the individual selector switches, thus rendering the individual selector switches operative to control the respective loud speaker circuits in the manner just stated. The master. switch has a number of additional positions equal to the number of program channels, and movement of the master switch into anyone of such additional positions effects distribution of program from one particular program channel to all of the loud speaker circuits irrespective of the settings of the individual selector switches.

The master switch is built up of a number of double pole sections, as described, and is provided with a plurality of positions, as described, the number of double pole sections and the number of positions each being one greater than the number of primary program channels; viz., n+1 where n is the number of program channels. The size of the master switch is thus determined by the number of program channels and-is independent of the number of load circuits included in the system. The master switch also carries means for making and breaking the load coil circuits in the manner described'above. Each individual selector switch comprises one double pole section and has a number of positions equal to the number of positions on the master switch; viz., n+1. Each switch also carries means for making and breaking load coil circuits in the manner described.

It will be understood that the invention is not limited specifically to the system described above and shown in the drawings by way of illustrating the invention. For instance, any desired number of program channels may be provided. All or any number of the individual switches may be placedat the loud speakers if desired or at any other point, instead of being centralized at one point as in the system shown. The mechanical construction and design of the switches and other elements of apparatus may be varied as desired. The system can be designed as described so that program from any desired one of the several program channels can be distributed by the master switch to all loud speakers in the system or, if desired, this arrangement may be provided for only certain ones of the several program channels. Also, if desired, the system may comprise certain loud speaker circuits which are not brought under the control of the master switch. If desired, additional connections (not shown) disconnected from all load circuits. Suitable connections through the master switch may be provided for utilizing these program channels for any purpose desired when the master switch is in such position that these channels would normally be dead. While the system has been described herein as a system of centralized radio, it is applicable generally as a system of electrical control wherein centralized control and distribution of energy from certain primary circuits to a plurality of load circuits is desired, and it is understood that the use in the claims of such terms as program channel, loud speaker circuits, and the like, are not necessarily limited strictly to radio but are intended to cover similar uses involving primary circuits and secondary or load circuits supplied therefrom. It will be understood that these and other modifications of the system may be made without departing from the invention as defined in the appended claims.

I-claim:

1. A centralized system of the character disclosed which comprises a plurality of primary circuits, a plurality of load circuits, an individual selector switch associated with each load circuit having a plurality of positions for the selection of a desired primary circuit, and a master switch having at least one position which serves to connect a plurality of said primary circuits to different respective positions of said individual selector switches, whereby the said individual selector switches are operative to select a desired primary circuit.

2. A centralized control system of the character disclosed which comprises a plurality of primary circuits, a plurality of load circuits, an individual selector switch associated with each load circuit having a plurality of positions for the selection of a desired primary circuit, and a master switch having at least one position which serves to connect a plurality of said primary circuits to difi'erent respective positions of said individual selector switches, whereby said individual selector switches become operative in the selection of a desired primary circuit, and having at least one other position which serves to connect one of said primary circuits to a plurality of difi'erent position on said individual selector switches.

3. A centralized electrical control system of the character disclosed which comprises a plurality of primary circuits, a plurality of load circuits, an individual selector switch associated with each load circuit having an off position for disconnecting the load circuit from active service and having a plurality of active positions for the selection of a desired primary circuit, and a master switch having one position which serves to connect the respective primary circuits to the respective active positions of 'said individual selector switches, whereby said individual selector switchesbecome operative in the selection of a desired primary circuit, and having a plurality of other positions each of which serves to connect one of said primary circuits with all of the respective positions of said individual selector switches, including the off position, and to disconnect all other primary circuits therefrom, whereby all of said load circuits can be energized simultaneously from any desired primary circuit selected by rea ers the master switch irrespective of the settings of the various individual selector switches.

4. A centralized radio system for selectively distributing program from a plurality of program channels to a plurality of loud speaker circuits, which comprises a plurality of program channels, a plurality of loud speaker circuits, an individual selector switch associated with each loud speaker circuit, and a master switch having a position for normally distributing programfrom all of said program channels to each individual selector switch so that the program for each loud speaker circuit can be selected by operation of the individual selector switch associated with that circuit, andhaving a plurality of additional positions each of which eilects distribution of program from. one of said program channels to all positions of said individual selector switches, thereby rendering said individual selector switches inoperative in the selection of program and placing program from one selected program channel on the several loud speaker circuits irrespective of the settings of the individual selector switches.

5. A centralized radio system of the character disclosed which comprises a plurality of loud speaker circuits, an individual selector switch associated with each of said loud speaker circuits having a number of active positions at least equal to the number of program channels from which program selection is desired, a master switch having a number of independent sections at least equal to the number of program channels from which program selection is desired, a plurality of program channels, connections between the several respective program channels and'the neutral position of the respective sections of said master switch, selector contacts for each section of said master switch, and connections between the respective selector contacts of said master switch and the respective positions of the several individual selector switches, whereby said neutral position of the master switch serves to connect the several program channels with the respective positions of the individual selector switches to thereby render the respective individual selector switches operative in the selection'of program for the respective loud speaker circuits.

6. A centralized radio system of the character disclosed which comprises a plurality of loud speaker circuits, an individual selector switch associated with each of said loud speaker circuits having a number of activepositions at least equal to the number of program channels from which program selection is desired, a master switch having a number of independent sections at least equal to the number of active positions provided on the respective individual switches, a plurality of program channels, connections between the several respective program channels and the neutral position of the respective sections of said master switch, selector contacts for each section of said master switch, connections between the respective selector contacts of said master switch and the respective positions of the several individual selector switches, and a plurality of additional positions provided on said master switch equal in number to the number of program channels all sections of said respective added positions of said master switch being connected in parallel and each of said positions being connected with its corresponding program channel and not connected with any other program channel, whereby the neutral position of said master switch eifects distribution of the several programs to the respective positions of the individual selector switches and the additional positions of said master switch efiect distribution of one selected program to the respective positions of the dividual selector switches and thereby render the individual switches inoperative in the selection of program.

7. A centralized radio system which comprises a plurality of loud'speakercircuits, an individual selector switch associated with each of said loud speaker circuits having a number of active positions equal to the number of program channels and an off position, a master switch having a number of independent sections one greater than the number of program channels, connections between the respective program channels and the neutral position of the respective sections of said master switch, selector contacts for each section of said master switch, connections between the respective selector contacts of said master switch and the respective positions of the several individual selector switches including the off" position, whereby said neutral position of the master switch serves to connect the several program channels with the respective active positions of the individual selector switches leaving the oil position unenergized,

and a plurality of additional positions provided tings of the individual selector switches.

8. A centralized radio system of, the class described which comprises a plurality of loud speaker circuits, at desired number n of program channels from which program selection is desired and to each of which simultaneous connection of loud speaker circuits may be desired, an individual selector switch associated with each loud speaker circuit having n+1 positions defined by stationary contacts and having a movable contact operating over said several positions, connections between the movable contact of each individual selector switch andsits corresponding loud speaker circuit, a master switch having n+1 double pole sections, each section comprising n+1 positions defined by stationary contacts, a movable contact operating over the several positions of each of said switch sections, the said movable contacts of the several switch sections being fixed relative to each other so that the contacts of all of the several sections lie in the same switch position at any one time and move simultaneously upon operation of the switch. permanent connections between the n program channels and the said stationary contacts of n of the n+1 sections of the master switch in the neutral position of the said switch, the stationary contacts of the neutral position of one section of the switclrremaining dead, permanent connections between the n+1 movable contacts of the master switch and the respective stationary contacts of the n+1 positions) of the individual selector switches, whereby the neutral position of the master switch connects the respecall loud speaker circuits irrespective of the settive program channels with the respective active positions of the individual selector switches and leaves the' fofi position dead, and permanent connections between the respective program channels and the stationary contacts of the remaining positions of the master switch, the contacts of each position being connected in parallel to one program channel and the different positions being connected respectively to the different programchannels, whereby each of the said remaining n positions of the master switch renders all individual selector switches inoperative and effects connection of one program channel to all loud speaker circuits irrespective of the settings of the individual-selector switches.

9. A centralized radio system of the character disclosed which comprises a plurality of program channels, a plurality of loud speaker cir-' cuits, an individual selector switch associated with each loud speaker circuit having an off position for disconnecting the loud speaker circuit from active service and having a plurality of active positions for selection of program, a plurality of load coils associated with each individual selector switch equal in number to the number of program channels normally available at that switch, each of said load coils being of impedance approximately equal to the effective impedance of the loud speaker circuit controlled by the said individual selector switch and the respective load coils being normally in circuit with the respective program channels,, means associated with said individual selector switch for disconnecting the corresponding load coil when the loud speaker circuit is connected to any program channel, thereby providing for substantially constant load on all program channels irrespective of the number of loud speaker circuits in operation and irrespective of the distribution of the loud speaker circuits among the several program channels, and a master switch having a position which serves to distribute program from the respective program channels to the respective active positions of said individual selector switches.

10. A centralized radio system of the character disclosed which comprises a plurality of program channels, a plurality of loud speaker circuits, an individual selector switch associated with each loud speaker circuit having an ofi position for disconnecting the loud speaker circuit from active service and having a plurality of active positions for selection of program, a plurality of load coils associated with each individual selector switch equal in number to the number of program channels normally available at that switch, each of said load coils being of impedance approximately equal to the effective impedance of the loud speaker circuit controlled by the said individual selector switch and the-respective load coils being normally in circuit with the respective program channels, means associated with said individual selector switch for disconnecting the corresponding load coil when the loud speaker circuit is connected to any program channel, thereby pro viding for substantially constant load on all program channels irrespective of the number of loud speaker circuits in operation and irrespective of the distribution of the loud speaker circuits among the several program channels, a master switch having one position which serves to connect the respective program channels to the respective active positions of said individual selector switches leaving the "01? position dead, whereby the individual selector switches are operative in the selection of program, and having a plurality of other positions each of which serves to connect one of said program channels with all of the respective positions of said individual selector switches including the off position and to disconnect all other primary circuits therefrom, whereby all of said loud speaker circuits can be energized simultaneously from one primary circuit selected by the master switch irrespective of the settings of the various individual selector switches, and means associated with the master switch for disconnecting all load coils simultaneously with the movement of said switch into the position which supplies the loud speaker circuits with program from one program channel.

11. A centralized radio system of the class described which comprises a plurality of loud speaker circuits, a desired number n of program channels from which program selection is desired and to each of which simultaneous connection of all loud speaker circuits may be desired, an individual selector switch associated with each loud speaker circuit having n+1 positions defined by stationary contacts and a movable contact operating over said several positions, connections be-,

tween the movable contact of each individual selector switch and its corresponding load circuit, a plurality of load coils associated with each individual selector switch equal in number to the number of program channels normally available at that switch, each of said load coils being of impedance approximately equal to the effective impedance of the loud speaker circuit controlled by the said individual selector switches and the respective load coils being normally in circuit with the respective program channels, means associated with said individual selector switch for disconnecting the corresponding load coil when the loud speaker circuit is connected to any program channel, thereby providing for substantially constant load on all program channels irrespective of the distribution of the loud speaker circuits among the several program channels, a master switch having n+1 double-pole sections, each section comprising n+1 positions defined by stationary contacts, a movable contact operating over the several positions of each of said switch sections, the said movable contacts of .the several switch sections being fixed relative to each other so that the contacts of all of the several sections lie in the same switch position at any one time and move simultaneously upon'operation of the switch, means associated with the master switch for disconnecting all load coils simultaneously with the movement of said switch into position to supply all loud speaker circuits with program from one program channel, permanent connections between the n program channels and the said stationary contacts of n of the n+1 sections of the master switch in the neutral position of the said switch, permanent connections between the n+1 movable contacts of the master switch and the respective stationary contacts of the several positions of the individual selector switches, whereby the neutral position of the master switch connects the respective program channels with the respective active positions of the individual selector switches and leaves the off position dead, and permanent connections between the respective program channels and the stationary contacts of the remaining n positions of the master switch, the contacts of each position being connected in parallel to one program channel and the different positions being connected respectively to the difierent program channels, whereby each of the said remaining 12. positions of the master switch renders all individual selector switches inoperative and efiects connection of one program channel to all loud speaker circuits irrespective of the settings of the individual selector switches.

, 12. A centralized radio system of the class described which comprises a plurality of loud speaker circuits, a desired number n of program channels from which program selection is desired and to each of which simultaneous connection of all loud speaker cir'cuits may be desired, an individual selector switch associated with each loud speaker circuit having n+1 positions defined by stationary contacts and having a movable con- -tact operating over said several positions, connections between the movable contact of each individual selector switch and its corresponding loud speaker circuit, a plurality of load coils associated with each individual selector switch equalin number to the number of program channels normally available at that switch, each of said load coils being of impedance approximately equal to the effective impedance of the loud speaker circuit controlled by the said individual selector switch and the respective load coils being normally in circuit with the respective program channels, means associated with said individual selector switch for disconnecting the corresponding load coil when the loud speaker circuit is connected to any program channel, thereby providing for substantially constant load on all program channels. irrespective of the number of loud speaker circuits in operation and irrespective of the distribution of the loud speaker circuits among the several program channels, a

master switch having n+1 double pole sections, each section comprising n+1 positions defined by stationary contacts anda movable contact operating over the several positions of .each of said switch sections, the moving contactsof the several switch sections being fixed relative to each other so that the contacts of all of the several sections lie in the same switch position at any onetime and move simultaneously upon operation of the switch, permanent connections between the n program channels and the said stationary contacts of n of the n+1 sections of the master switch in a neutral position of the said switch, permanent connections between the n+1 movable contacts of the master switch and the respective stationary contacts of the several positions of the individual selector switches, whereby the neutral position of the master switch connects the respective program channels with the respective active positions of the individual selector switches and leaves the o position dead, permanent connections between the 11 program channels and the stationary contacts of the n+1 double pole sections of the remaining n positions of the master switch, the contacts of each position being connected in parallel to one program channel and the different positions being connected respectively to the different program channels, whereby each of the said remaining n positions of the master switch renders. all individual selector switches inoperative and effects connection of one program channel to all loud speaker circuits irrespective of the settings of the individual selector switches, and a common lead for one side of all of the load coils which are associated with each respective program channel, n additional single pole sections provided on said master switch having their respective movable contacts connected in the respective common load coil leads and having the respective stationary contacts of the neutral position of the switch likewise connected in the respective common load coil leads, whereby the neutral position of the master switch connects all of said load coils in circuit and renders the individual selector switches operative in controlling said load coils while all other positions of the master switch eifect disconnection of all load coils from the circuit.

13. A centralized radio system for selectively distributing program from a plurality of program channels to a plurality of loud speaker circuits, which comprises a plurality of program channels, a plurality of loud speaker circuits, an individual selector switch associated with each loud speaker circuit, a master s witch having a position for normally distributing program from all of said program channels to each individual selector switch sothat the program for each loud speaker circuit can be selected by operation of the individual selector switch associated with that circuit, and having a plurality of additional positions each of which effects distribution of program from one of said program channels to all positions of said individual selector switches, therebyrendering saidindividual selector switches inoperative in the selection of program and plac ing program from one selected program channel on the s veral loud speaker circuits irrespective of the se ings of the individual selector switches, the remaining program channels being dead, and additional contacts and connections provided on said master switch for. effecting connection, when the master switch is in position to connect a selected program channel with all loud speaker circuits, between a normally dead program channel and any desired input and output circuits. whereby the said normally dead program channel may be usefully employed.

JAMES LEONARD E I 

